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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => Lighting FUD Forum Archive => Topic started by: ThomasA(lbenberger) on April 26, 2004, 02:59:42 am

Title: dimmer and 3phase power
Post by: ThomasA(lbenberger) on April 26, 2004, 02:59:42 am
Hi everybody!

First of all let me apologize for such a basic question but I am coming from the audio side of the business and I did not have too much to do with lighting yet.

OK, my question is: If I have a dimmer pack - say 12x10A max. 230V - with a tree-phase power plug (3x32A 230V), does the dimmer divide the 3 phases to dedicated channels, eg. first phase serves channel 1-4, second phase serves 5-8,...

Or does the dimmer provide all the available current to wherever it is needed at the moment?

I'm afraid this was a bit unclear, so here is my problem:

If I plug six pairs of PAR64 (1kW) into one channel each of a dimmer with a 3phase 32A 230V plug, does it matter if it is channels 1-6 or channels 1, 2, 5, 6 and 9, 10?

I have analogue lights on a 3x32A dimmer that draw a total of approximately 60 Amperes. In addition to that I want to cold-plug some lights like color changers or disco FX that draw a maximum of 25 Amperes. Can I somehow make sure that I have equal load and do not exceed the maximum current draw on all of the 3 phases? Can I for example make a dimmer use only two phases of the three phase power and leave the third one to the lights I don't need a dimmer for?

If this was possible I could specify only one 3x32A circuit, otherwise I would have to get an additional 3x16A circuit.

Thanks very much for your help, and sorry again for such basic questions! I wish there was a studyhall for lights on PSW as well...

Cheers, Thomas

BTW: I am planning this for a mobile lights system in Austria and I did not have a look at any specific brands or models of dimmers yet. If there are any brands that offer what I am looking for while others do not, please let me know!
Title: Re: dimmer and 3phase power
Post by: TJ (Tom) Cornish on April 26, 2004, 10:26:08 am
I'm fairly sure that most dimmers don't have some kind of auto phase switching mechanism.  That would be complicated and expensive, and not really of that much value anyway.

I own an ETC Smartpack 1210 which is very similar to what you describe - 12 10 amp channels, designed for a 3-phase 40A input.  Internally device is split into 6 power busses with two adjacent channels per bus.  The pack has 5 input terminals where you attach whatever feed power source you have to - 3 "hots" one neutral and one ground.  The dimming busses can be manually wired to any of the hot terminals.  The default 3-phase mode is the wires from channels 1-2 and 3-4 are on phase A, the wires from 5-6 and 7-8 are on phase B, and 9-10 and 11-12 are on phase C.

If you wanted to wire it to be split phase (I'm not sure if you have this in Australia) you can take the 5-6 wire and put it on the phase A terminal, and the 7-8 wire and put it on the phase C terminal, and now the pack is set up to run with a 60-amp two-phase input.

Any load balancing is manual - i.e. if I try to put a 2000 watt lamp on one of my 10A channels, I'm going to trip that channel's breaker.  

For your example 1, you probably should spread the load across all 12 channels if it's all the same to you, but phase load balancing usually just works itself out in the sense that usually you use most of the dimmer channels you have.

Are you saying that each of the par64s is a 1KW fixture and that you are trying to run a pair of of 1 10A channel?  That won't work.  You'll have to split your cans so that you have less than 1200 watts per dimmer channel.

To sum this all up, you have to stay under the max load for any device and it's your job to sort out where the power comes from.  If you get a dimmer like the Smarpack (and probably others) you would be able to set it to two phase mode, but make sure you understand what you are doing and have safe electrical equipment in compliance with local codes.

Title: Re: dimmer and 3phase power
Post by: ThomasA(lbenberger) on April 26, 2004, 11:22:19 am
Thanks for the quick reply!

First of all - Austria was no typo, I'm currently in Australia but designing the system for Austria, not that it matters because the electrical system is about the same here down under.

Secondly, I'm not sure why I can't put 2kW on one 10A circuit if I was in the 230V part of the world. I guess you were refering to the American voltages, and for me 2000W/230V = 8,7A is true or am I missing something (as I said in the other post, I don't have too much experience in that)?

And third, you answered both of my questions, thank you for that!

Let me just repeat what you said in my own words, to see if I really have grasped it:

Your 12x10A dimmer pack has dedicated channels for the 3 phases of the power service. The P1 connector serves channel 1-4, P2 5-8 and P3 9-12, each together with neutral of course.

So if I needed only 8 dimmer channels, I could simply not connect P3 to the dimmer but take it and split neutral as well as ground for another circuit with all of my lights that don't require a dimmer. I'm assuming that I run all the three phases through breakers as well as together with neutral through an RCD before the dimmer.

Or if I made the split and wanted to have access to the remaining dimmer channels 9-12 I could connect P2 to the inputs of channels 5-8 AND 9-12 which would give me power to all of the dimmer channels, but with only 32A available for all of the channels 5-12 together. Is this true?

I have not yet decided on my setup, but relying on only one 230V/32A three phase outlet is important for me. Therefore I could go with 6x PAR64 1kW on the first 3 channels (8,7A per channel, approx. 26A total), some PAR36 Pinspots or other small stuff on channel 4 and 16x PAR56 300W on channels 5-12 with 2 fixtures per channel (2,6A per channel, 21A total).

This would leave me the 32A of P3+neutral for the colour changers and Disco-FX.

I hope I got it right, a confirmation would be appreciated and thanks for your help!


BTW: This is for a mobile installation, but in a fixed setup where nothing is changed from gig to gig and nobody has access to the wiring. Electrical safety is important of course, but at the same time I don't have to cater for changing setups - I can be 100% sure that nobody touches the wirings I make.
Title: Re: dimmer and 3phase power
Post by: TJ (Tom) Cornish on April 26, 2004, 01:29:12 pm
You'll have to excuse my lack of knowledge of non-American systems, so take what I say with that being understood.

I will be in over my head if I start giving you advice as to what would be legal or safe, but to answer your question, yes, theoretically you could split the third phase off and use it outside the dimmer.  

That being said, it seems to me that you are in need of a power distro where you could more safely split out the third phase and breaker it separately from the dimmer you are using.
Title: Re: dimmer and 3phase power
Post by: ThomasA(lbenberger) on April 27, 2004, 11:35:34 pm
Thanks very much for your input!

I'll get or build a power distro for what I described in the other post.

Cheers, Thomas